Japanese Unexamined Patent Applications Shou-51-57011 and Hei-2-215997 disclose a vane wheel divided into two independent parts, with the parts being subsequently joined to each other. Japanese Unexamined Patent Application Shou-51-57011, proposes a vane wheel dividing line extending perpendicularly to a rotational axis of the vane wheel; Japanese Unexamined Patent Application Hei-2-215997, proposes an arrangement wherein the vane wheel dividing line extends along edges of vanes.